x-ring

The X-ring chain is a specialized type of sealed roller chain used to transfer mechanical power. Like the standard O-ring chains it is also used in high performance motorcycles. It uses X-ring seal to keep lubricant (usually grease) in place.
It has higher performance (in terms of durability, lifetime, and power loss) than non-O-ring chains as it has less friction than O-ring chain while providing adequate lubrication and protection against foreign elements which also increases reliability. It can last twice as long as the O-ring chain under some circumstances.

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